Polishing liquid and polishing method

ABSTRACT

A polishing liquid which is used for chemical mechanical polishing of a body to be polished in a planarization process for manufacturing of a semiconductor integrated circuit, the body to be polished including at least a first layer containing polysilicon or modified polysilicon and a second layer containing at least one selected from the group consisting of silicon oxide, silicon nitride, silicon carbide, silicon carbonitride, silicon oxycarbide, and silicon oxynitride, the polishing liquid having a pH of 1.5 to 7.0, including (1) colloidal silica particles, (2) an organic acid, and (3) an anionic surfactant, and being capable of selectively polishing the second layer with respect to the first layer.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority under 35 USC 119 from Japanese PatentApplication No. 2008-143468, the disclosure of which is incorporated byreference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a polishing liquid used in a process ofproducing a semiconductor integrated circuit and a polishing methodusing the same. More specifically, the present invention relates to apolishing liquid that can be preferably used for the formation of a gateon a semiconductor substrate and a polishing method using the same. Inparticular, the present invention relates to a polishing liquid forpolishing a semiconductor substrate having a layer containingpolysilicon or modified polysilicon by chemical mechanical polishing anda polishing method using the same.

2. Description of the Related Art

In recent years, in the development of semiconductor devices such as asemiconductor integrated circuit (hereinafter sometimes referred to asan “LSI”), high density and high integration by miniaturization andlamination of wiring have been required in order to realize reduced sizeand high speed. As a technique for achieving the above, varioustechniques, such as chemical mechanical polishing (hereinafter sometimesreferred to as “CMP”), have been used. CMP is an essential technique atthe time of planarizing the surface of films to be processed such as aninterlayer insulating film, plug formation, formation of embedded metalwiring, or the like, and thereby smoothing of a substrate or the like isperformed.

A usual CMP process includes: adhering a polishing pad onto a circularpolishing platen; immersing the surface of the polishing pad in apolishing liquid; pressing the surface (surface to be polished) of asubstrate (wafer) against the pad, and rotating both the polishingplaten and the substrate while a given pressure (polishing pressure) isapplied thereto from the rear face to planarize the surface of thesubstrate by the mechanical friction generated.

In recent years, CMP has been increasingly applied to respectiveprocesses in semiconductor manufacturing. For example, CMP is applied toa gate formation process in the manufacturing of transistors.

In conventional transistors, a gate mainly containing modifiedpolysilicon in which impurities, such as B, are doped in polysilicon,has been manufactured. However, in transistors after the 45 nmgeneration, the use of a gate insulating film with a high dielectricconstant (High-k film) and a metal gate electrode in place ofconventional polysilicon has been examined so as to achieve bothreduction in power consumption during a standby state and high currentdriving ability. Some techniques to which these have been applied havebeen proposed. For example, a method has been proposed which includes:forming a dummy gate insulating film and a dummy gate electrode; dopingimpurities into a polycrystalline silicon film in a self-alignmentmanner to form a source-drain diffusion layer; removing the dummy gateinsulating film and the dummy gate electrode; and then forming a gateinsulating film with a high dielectric constant and a metal gateelectrode (e.g., Japanese Patent Application Laid-Open (JP-A) Nos.2006-339597, 2006-344836, and 2007-12922).

Further, some techniques for forming a metal gate electrode have beenproposed. As one example thereof, there is a fully silicided gate(hereinafter referred to as a “FUSI gate”). The FUSI gate is formed bysiliciding a gate electrode formed with polysilicon in the same manneras in a conventional CMOS process. Conventionally, only the upper partof a gate electrode is silicided, but in the FUSI gate, the entire gateelectrode is silicided. Since the technique of the conventional CMOSprocess is useful in the case of the FUSI gate compared with the case offorming a metal gate electrode by a damascene process, the FUSI gate isadvantageous in terms of process construction.

In recent years, it has been proposed to, in such formation of a gateusing polysilicon or modified polysilicon (hereinafter sometimescollectively referred to simply as “polysilicon or the like”),selectively perform CMP with respect to the polysilicon or the like andsecond and third materials covering the periphery thereof (e.g., JP-A2005-93816). However, when a body to be polished containing polysiliconor the like is polished by CMP using a known polishing liquid, therearises a problem that the polysilicon or the like which is intended toremain as a gate material is excessively polished. This problem has ledto, for example, deterioration in performance of the obtained LSI.

SUMMARY OF THE INVENTION

According to an aspect of the invention, there is provided a polishingliquid which is used for chemical mechanical polishing of a body to bepolished in a planarization process for manufacturing of a semiconductorintegrated circuit, the body to be polished comprising at least a firstlayer containing polysilicon or modified polysilicon and a second layercontaining at least one selected from the group consisting of siliconoxide, silicon nitride, silicon carbide, silicon carbonitride, siliconoxycarbide, and silicon oxynitride,

the polishing liquid having a pH of 1.5 to 7.0, comprising (1) colloidalsilica particles, (2) an organic acid, and (3) an anionic surfactant,and being capable of selectively polishing the second layer with respectto the first layer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing changes in polishing rate of polysilicon whenthe pH of the polishing liquid containing an anionic surfactant wasvaried.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, the polishing liquid and the polishing method using thesame according to the invention are described in detail.

[Polishing Liquid]

The polishing liquid of the present invention is a polishing liquidwhich is used for chemical mechanical polishing of a body to be polishedin a planarization process for manufacturing of a semiconductorintegrated circuit, the body to be polished comprising at least a firstlayer containing polysilicon or modified polysilicon and a second layercontaining at least one selected from the group consisting of siliconoxide, silicon nitride, silicon carbide, silicon carbonitride, siliconoxycarbide, and silicon oxynitride,

the polishing liquid having a pH of 1.5 to 7.0, comprising (1) colloidalsilica particles, (2) an organic acid, and (3) an anionic surfactant,and being capable of selectively polishing the second layer with respectto the first layer.

In the present invention, the “polishing liquid” encompasses not only apolishing liquid when used for polishing (i.e., a polishing liquid whichhas been diluted as required) but a concentrated liquid of the polishingliquid. The concentrated liquid or the concentrated polishing liquidrefers to a polishing liquid in which the concentration of the solutehas been adjusted to be higher than that of the polishing liquid whenused for polishing, and is diluted with water or an aqueous solutionbefore used for polishing. The dilution ratio is generally 1 to 20 timesin volume. In this specification, the terms “concentrated” and“concentrated liquid” are used as idiomatic expressions which mean“having a higher concentration” and a “liquid having a higherconcentration” than when used for polishing, and are used in a differentmeanings from the general meanings in which a physical concentrationoperation such as evaporation is carried out.

The polishing liquid of the invention is preferably used whenpolysilicon or modified polysilicon is used as an electrode material anda gate electrode in a semiconductor integrated circuit is formed by CMP.More specifically, the polishing liquid of the invention is a polishingliquid which is used for chemical mechanical polishing of a body to bepolished in a planarization process for manufacturing of a semiconductorintegrated circuit, the body to be polished at least comprising a firstlayer containing polysilicon or modified polysilicon and a second layercontaining at least one selected from the group consisting of siliconoxide, silicon nitride, silicon carbide, silicon carbonitride, siliconoxycarbide, and silicon oxynitride.

The polishing liquid of the invention contains the above components (1),(2) and (3) and has a pH of 1.5 to 7.0. Thus, the second layercontaining at least one selected from the group consisting of siliconoxide, silicon nitride, silicon carbide, silicon carbonitride, siliconoxycarbide, and silicon oxynitride can be selectively polished withrespect to the first layer containing polysilicon or modifiedpolysilicon.

Regarding the selective polishing of the second layer with respect tothe first layer, it is preferable that the polishing liquid of thepresent invention can polish the body to be polished at a ratiorepresented by RR(other)/RR(p-Si) in the range of 1.5 to 200 whereinRR(p-Si) represents a polishing rate of the first layer and RR(other)represents a polishing rate of the second layer. More preferably, theratio represented by RR(other)/RR(p-Si) is in the range of 3 to 100.When the ratio represented by RR(other)/RR(p-Si) is in theabove-mentioned range, undesirable polishing of the first layer can besuppressed, and uneven separation of the first layer due to an excessivestress to be applied to the film interface between the first layer andthe underlayer at the time of polishing also can be effectivelysuppressed.

Therefore, by using the polishing liquid of the invention, the gateelectrode is not excessively polished but a layer containing siliconmaterials other than polysilicon or modified polysilicon that isrequired to be rapidly polished can be rapidly polished even when thegate electrode containing polysilicon or modified polysilicon is formedby CMP in manufacturing of LSI.

Hereinafter, each component constituting the polishing liquid of theinvention will be described in detail.

[(1) Colloidal Silica Particles]

The polishing liquid of the invention contains colloidal silicaparticles as at least a part of abrasive grains. The colloidal silicaparticles are preferably colloidal silica particles which do not containimpurities, such as alkali metal, in the particles and are obtained byhydrolysis of alkoxysilane. In contrast, colloidal silica particlesproduced by a method involving removing alkali from an aqueous alkalisilicate solution also can be used. However, in this case, alkali metalremaining inside the particles may be gradually eluted to influence thepolishing ability. From such a viewpoint, colloidal silica particlesobtained by hydrolysis of alkoxysilane are more preferable as a rawmaterial.

The particle diameter of the colloidal silica particles is suitablyselected according to the purpose of use. The average primary particlediameter of the colloidal silica particles is preferably in the range of5 nm to 100 nm, more preferably in the range of 10 nm to 100 nm, andstill more preferably in the range of 10 nm to 80 nm. The averagesecondary particle diameter of the colloidal silica particles ispreferably in the range of 10 nm to 300 nm, more preferably in the rangeof 20 nm to 300 nm, and still more preferably in the range of 20 nm to200 nm.

The colloidal silica particles in the invention particularly preferablyhas an average primary particle diameter of 5 nm to 100 nm and anaverage secondary particle diameter of 10 nm to 300 nm.

When the particle diameter of the colloidal silica particles satisfiesthe above-mentioned ranges, the generation of polishing damage can beeffectively suppressed.

Here, the average primary particle diameter of the colloidal silicaparticles in the invention refers to the particle diameter at a pointwhere the cumulative frequency of a particle-size accumulation curveobtained in terms of volume is 50%.

The average primary particle diameter of the colloidal silica particlescan be measured with an electron microscope (transmission type) or thelike.

The average particle diameter of the secondary particles formed bypartial aggregation of the colloidal silica particles (average secondaryparticle diameter) refers to an average particle diameter determined inthe particle size distribution obtained by dynamic light scatteringmethod. As a measuring apparatus for determining the particle sizedistribution, LB-500 manufactured by Horiba is used, for example.

The content (concentration) of the colloidal silica particles in thepolishing liquid of the invention is preferably 0.1% by mass to 10% bymass , more preferably 0.5% by mass to 10% by mass, and still morepreferably 1% by mass to 8% by mass, based on the total mass of thepolishing liquid when used for polishing. More specifically, the contentof the colloidal silica particles is preferably 0.1% by mass or morefrom the viewpoint of achieving a sufficient polishing rate, butpreferably 10% by mass or less from the viewpoint of effectivelysuppressing the occurrence of polishing damage.

In the polishing liquid of the invention, abrasive grains other than thecolloidal silica particles can also be used insofar as the effects ofthe invention are not impaired. However, in such a case, the proportionof the colloidal silica particles to all the abrasive grains ispreferably 50% by mass or more and particularly preferably 80% by massor more. All the abrasive grains contained in the polishing liquid maybe the colloidal silica particles.

In the polishing liquid of the invention, examples of the abrasivegrains that can be used in combination with the colloidal silicaparticles include fumed silica, ceria, alumina, and titania. The size ofthe abrasive grains is preferably not less than the size of thecolloidal silica particles but not more than twice the size of thecolloidal silica particles.

[(2) Organic Acid]

The polishing liquid of the invention contains at least one organicacid.

The organic acid as used herein serves as an oxidation promoter, pHadjuster, or a buffer, rather than a metal oxidizing agent. As theorganic acid, water-soluble organic acids are preferable. Examplesinclude water-soluble organic acids or amino acids. As examples of theorganic acids or amino acids, substances selected from the followinggroups are more suitable, for example.

More specifically, examples of the organic acids include formic acid,acetic acid, propionic acid, butyric acid, valeric acid, 2-methylbutyricacid, n-hexanoic acid, 3,3-dimethylbutyric acid, 2-ethylbutyric acid,4-methylpentanoic acid, n-heptanoic acid, 2-methylhexanoic acid,n-octanoic acid, 2-ethylhexanoic acid, benzoic acid, glycolic acid,salicylic acid, glyceric acid, oxalic acid, malonic acid, succinic acid,glutaric acid, adipic acid, pimelic acid, maleic acid, phthalic acid,malic acid, tartaric acid, citric acid, lactic acid,hydroxyethyliminodiacetic acid, iminodiacetic acid, acetamidoiminodiacetic acid, nitrilotripropanoic acid, nitrilotrimethylphosphonicacid, dihydroxyethyl glycine, tricine, and ammonium salts or alkalinemetal salts thereof, or mixtures thereof.

Examples of the amino acids include glycine, L-alanine, β-alanine,L-2-aminobutyric acid, L-norvaline, L-valine, L-leucine, L-norleucine,L-isoleucine, L-alloisoleucine, L-phenylalanine, L-proline, sarcosine,L-ornithine, L-lysine, taurine, L-serine, L-threonine, L-allothreonine,L-homoserine, L-thyrosin, 3,5-diiodo-L-thyrosin,β-(3,4-dihydroxyphenyl)-L-alanine, L-thyroxine, 4-hydroxy-L-proline,L-cysteine, L-methionine, L-ethionine, L-lanthionine, L-cystathionine,L-cystine, L-cysteine acid, L-asparatic acid, L-glutamic acid,S-(carboxymethyl)-L-cysteine, 4-aminobutyric acid, L-asparagine,L-glutamine, azaserine, L-arginine, L-canavanine, L-citrulline,δ-hydroxy-L-lysine, creatine, L-kynurenine, L-histidine,1-methyl-L-histidine, 3-methyl-L-histidine, ergothioneine, L-tryptophan,actinomycin C1, apamin, angiotensin I, angiotensin II, and antipain.

Among the organic acids, from the viewpoint of achieving a sufficientpolishing rate ratio, organic acids having at least one carboxyl groupin the molecular structure are preferable. Among the above, compoundsrepresented by the following Formula (I) are preferable.

HOOC—R—COOH   (I)

In Formula (I), R represents an alkylene group having 1 to 20 carbonatoms, an alkynylene group, a cycloalkylene group, an arylene group, ora group obtained by combining two or more thereof.

Examples of an alkylene group having 2 to 20 carbon atoms represented byR include an ethylene group, a propylene group, a butylene group, apentylene group, a hexylene group, a heptylene group, and an octylenegroup. Among the above, the ethylene group, the propylene group, and thebutylene group are preferable.

As an alkynylene group represented by R, alkynylene groups having 2 to10 carbon atoms are preferable. Specific examples include an ethynylenegroup and a propynylene group.

Examples of a cycloalkylene group represented by R include acyclohexylene group and a cyclopentylene group. Among the above, thecyclohexylene group is preferable.

Specific examples of an arylene group represented by R include aphenylene group and a naphthylene group. Among the above, the phenylenegroup is preferable.

Each group represented by R may further have a substituent. Examples ofthe substituent that can be introduced include a hydroxyl group, anamino group, a carboxyl group, a phosphoric acid group, an imino group,a thiol group, a sulfo group, and a nitro group.

Specific examples of the compound represented by Formula (I) includenitrilotriacetic acid, diethylenetriamine pentaacetic acid,ethylenediamine tetraacetic acid, oxalic acid, malonic acid, succinicacid, glutaric acid, adipic acid, pimelic acid, maleic acid, phthalicacid, malic acid, tartaric acid, citric acid, diglycolic acid,2-furancarboxylic acid, 2,5-furandicarboxylic acid, 3-furancarboxylicacid, 2-tetrahydrofurancarboxylic acid, diglycolic acid, methoxyaceticacid, methoxyphenylacetic acid, and phenoxyacetic acid, or mixturesthereof. Among the above, from the viewpoint of achieving a favorableselectivity, ethylenediamine tetraacetic acid, oxalic acid, malonicacid, succinic acid, glutaric acid, adipic acid, pimelic acid, maleicacid, phthalic acid, malic acid, tartaric acid, citric acid, anddiglycolic acid are preferable, and oxalic acid, adipic acid, pimelicacid, maleic acid, malic acid, tartaric acid, citric acid, anddiglycolic acid are more preferable.

The organic acid contained in the polishing liquid may be only one kind,or two or more kinds thereof may be used in combination.

The content of the organic acid in the polishing liquid is preferably0.0001% by mass to 10% by mass, more preferably 0.001% by mass to 1% bymass, and still more preferably 0.01% by mass to 1% by mass based on themass of the polishing liquid when used for polishing. More specifically,from the viewpoint of achieving a sufficient polishing rate, the contentof the organic acid is preferably 0.0001% by mass or more. From theviewpoint of maintaining favorable flatness, the content of the organicacid is preferably 10% by mass or lower.

[(3) Anionic Surfactant]

The polishing liquid of the invention contains an anionic surfactant.

Examples of the anionic surfactant include sulfonate, carboxylate,sulfate, and phosphate. Among the above, from the viewpoint of achievinga favorable polishing rate selectivity, sulfonate is preferable.

More specifically, examples of sulfonate include alkylsulfonate,sulfosuccinate, α-olefin sulfonate, and N-acylsulfonate.

Examples of carboxylate include soap, N-acylamino acid salt,polyoxyethylene, or polyoxypropylene alkyl ether carboxylate, and acylpeptide.

Examples of sulfate include sulfated oil, alkyl sulfate, alkyl ethersulfate, polyoxyethylene or polyoxypropylene alkyl allyl ether sulfate,and alkylamide sulfate.

Examples of phosphate include alkyl phosphate and polyoxyethylene orpolyoxypropylene alkyl allyl ether phosphate.

From the viewpoint of achieving a favorable polishing rate selectivity,examples of a preferable anionic surfactant contained in the polishingliquid include at least one compound selected from the group consistingof compounds represented by the following Formulae (II), (III), (IV),and (V).

Hereinafter, these compounds will be described.

R¹—O—SO₃X   Formula (II)

In Formula (II), R¹ represents an alkyl group having 6 to 30 carbonatoms, an alkenyl group, a cycloalkyl group, an aryl group, an aralkylgroup, or a group obtained by combining two or more thereof, and Xrepresents a hydrogen atom, sodium, potassium, ammonium, diethanolamine,or triethanolamine.

Specific examples of the alkyl group having 6 to 30 carbon atomsrepresented by R¹ include a decyl group, a dodecyl group, a tetradecylgroup, a hexadecyl group, an octadecyl group, an icosyl group, and atriacontyl group. Among the above, the dodecyl group, the tetradecylgroup, the hexadecyl group, and the octadecyl group are preferable.

As the alkenyl group represented by R¹, alkenyl groups having 6 to 30carbon atoms are preferable. Specific examples include a decenyl group,a dodecenyl group, a tetradecenyl group, a hexadecenyl group, anoctadecenyl group, an icosenyl group, and a triacontenyl group. Amongthe above, the dodecenyl group, the tetradecenyl group, the hexadecenylgroup, or the octadecenyl group is preferable.

As the cycloalkyl group represented by R¹, a cyclohexyl group and analkyl-substituted cyclohexyl group are preferable.

Specific examples of the aryl group represented by R¹ include a phenylgroup and a naphthyl group. Among the above, the phenyl group ispreferable.

The substituent represented by R¹ may further have a substituent.Examples of the substituent that can be introduced include a hydroxygroup, an amino group, a carboxyl group, a phosphoric acid group, animino group, a thiol group, a sulfo group, and a nitro group.

X represents a hydrogen atom, sodium, potassium, ammonium,diethanolamine, or triethanolamine, with sodium, ammonium, adiethanolamine, or triethanolamine being preferable.

The compounds represented by Formula (II) can have a structure of a highmolecular weight compound having such a partial structure. There is nolimitation on the “polymer containing the partial structure representedby Formula (II)” insofar as it is structured such that the substituentrepresented by R¹ in Formula (II) is combined to the main chain or formsa part of the main chain. For example, high molecular weight compoundsin which a structural unit having the structure represented by Formula(II) at the side chain has been polymerized are mentioned. In this case,the degree of polymerization is preferably from 2 to 10 and morepreferably from 2 to 5.

R²—O—(CH₂CH₂O)_(n)—SO₃X   Formula (III)

In Formula (III), R² represents an alkyl group having 6 to 30 carbonatoms, an alkenyl group, a cycloalkyl group, an aryl group, an aralkylgroup, or a group obtained by combining two or more thereof, nrepresents an integer of 1 to 10, and X represents a hydrogen atom,sodium, potassium, ammonium, diethanolamine, or triethanolamine.

Specific examples of the alkyl group having 6 to 30 carbon atomsrepresented by R² include a decyl group, a dodecyl group, a tetradecylgroup, a hexadecyl group, an octadecyl group, an icosyl group, and atriacontyl group. Among the above, the dodecyl group, the tetradecylgroup, the hexadecyl group, and the octadecyl group are preferable.

As the alkenyl group represented by R², alkenyl groups having 6 to 30carbon atoms are preferable. Specific examples include a decenyl group,a dodecenyl group, a tetradecenyl group, a hexadecenyl group, anoctadecenyl group, an icosenyl group, and a triacontenyl group. Amongthe above, the dodecenyl group, the tetradecenyl group, the hexadecenylgroup, or the octadecenyl group is preferable.

As the cycloalkyl group represented by R², a cyclohexyl group and analkyl-substituted cyclohexyl group are preferable.

Specific examples of the aryl group represented by R² include a phenylgroup and a naphthyl group. Among the above, the phenyl group ispreferable.

The substituent represented by R² may further have a substituent.Examples of the substituent that can be introduced include a hydroxygroup, an amino group, a carboxyl group, a phosphoric acid group, animino group, a thiol group, a sulfo group, and a nitro group.

n in Formula (III) is an integer of 1 to 10, and from the viewpoint ofmaintaining a favorable stability over time, it is preferably an integerof 1 to 8, and more preferably an integer of 1 to 5.

X represents a hydrogen atom, sodium, potassium, ammonium,diethanolamine, or triethanolamine, with sodium, ammonium, adiethanolamine, or triethanolamine being preferable.

In Formula (IV), R³ represents an alkyl group having 6 to 30 carbonatoms, an alkenyl group, a cycloalkyl group, an aryl group, an aralkylgroup, or a group obtained by combining two or more thereof, and Xrepresents a hydrogen atom, sodium, potassium, ammonium, diethanolamine,or triethanolamine.

Specific examples of the alkyl group having 6 to 30 carbon atomsrepresented by R³ include a decyl group, a dodecyl group, a tetradecylgroup, a hexadecyl group, an octadecyl group, an icosyl group, and atriacontyl group. Among the above, the dodecyl group, the tetradecylgroup, the hexadecyl group, and the octadecyl group are preferable.

As the alkenyl group represented by R³, alkenyl groups having 6 to 30carbon atoms are preferable. Specific examples include a decenyl group,a dodecenyl group, a tetradecenyl group, a hexadecenyl group, anoctadecenyl group, an icosenyl group, and a triacontenyl group. Amongthe above, the dodecenyl group, the tetradecenyl group, the hexadecenylgroup, or the octadecenyl group is preferable.

As the cycloalkyl group represented by R³, a cyclohexyl group and analkyl-substituted cyclohexyl group are preferable.

Specific examples of the aryl group represented by R³ include a phlenylgroup and a naphthyl group. Among the above, the phenyl group ispreferable.

The substituent represented by R³ may further have a substituent.Examples of the substituent that can be introduced include a hydroxygroup, an amino group, a carboxyl group, a phosphoric acid group, animino group, a thiol group, a sulfo group, and a nitro group.

X represents a hydrogen atom, sodium, potassium, ammonium,diethanolamine, or triethanolamine, with sodium, ammonium, adiethanolamine, or triethanolamine being preferable.

In Formula (V), R⁴ represents an alkylene group having 1 to 20 carbonatoms, an alkynylene group, a cycloalkylene group, an arylene group, analkylene oxide group, or a group obtained by combining two or morethereof.

Specific examples of the alkylene group having 1 to 20 carbon atomsrepresented by R⁴ include a methylene group, an ethylene group, apropylene group, a butylene group, a decylene group, and a dodecylenegroup. Among the above, the methylene group, the ethylene group, and thepropylene group are preferable.

As the alkynylene group represented by R⁴, alkynylene groups having 1 to20 carbon atoms are preferable. Specific examples include a methynylenegroup, an ethynylene group, a propynylene group, a butynylene group, adecynylene group, and a dodecynylene group. Among the above, themethynylene group, the ethynylene group, and the propynylene group arepreferable.

As the cycloalkylene group represented by R⁴, a cyclohexylene group andan alkyl-substituted cyclohexylene group are specifically preferable,for example.

Specific examples of the arylene group represented by R⁴ include aphenylene group and a naphthylene group. Among the above, the phenylenegroup is preferable.

As the alkylene oxide group represented by R⁴, an ethylene oxide groupor a propylene oxide group is preferable. The alkylene oxide group maybe, for example in the case of an ethylene oxide group, a group whichconsists of one ethylene oxide unit or a plurality of ethylene oxideunits (n is 2 or more in (CH₂CH₂O)_(n)). In the case of the group whichconsists of a plurality of ethylene oxide units, n is preferably in therange of from 2 to 10.

The linking group represented by R⁴ may further have a substituent.Examples of the substituent that can be introduced include a hydroxygroup, an amino group, a carboxyl group, a phosphoric acid group, animino group, a thiol group, a sulfo group, and a nitro group.

In Formula (V), R⁵ to R⁹ each independently represent a hydrogen atom, ahydroxy group, an alkyl group having 1 to 30 carbon atoms, an alkenylgroup, a cycloalkyl group, an aryl group, an aralkyl group, a sulfogroup, a carboxy group, or a hydrocarbon group containing any of thesegroups.

Specific examples of the alkyl group having 1 to 30 carbon atomsrepresented by R⁵ to R⁹ include a methyl group, an ethyl group, a propylgroup, a butyl group, a hexyl group, a heptyl group, an octyl group, anonyl group, a decyl group, a dodecyl group, a tetradecyl group, ahexadecyl group, an octadecyl group, an icosyl group, and a triacontylgroup.

Specific examples of the alkenyl group represented by R⁵ to R⁹ include adecenyl group, a dodecenyl group, a tetradecenyl group, a hexadecenylgroup, an octadecenyl group, an icosenyl group, and a triacontenylgroup.

As the cycloalkyl group represented by R⁵ to R⁹, a cyclohexyl group andan alkyl-substituted cyclohexyl group are preferable.

Specific examples of the aryl group represented by R⁵ to R⁹ include aphenyl group and a naphthyl group. Among the above, the phenyl group ispreferable.

The substituent represented by R⁵ to R⁹ may further have a substituent.Examples of the substituent that can be introduced include a hydroxygroup, an amino group, a carboxyl group, a phosphoric acid group, animino group, a thiol group, a sulfo group, and a nitro group.

Among them, preferable examples of R⁵ to R⁹ are a hydrogen atom, analkyl group having 1 to 20 carbon atoms, a hydroxy group, a sulfo group,a carboxy group, and a hydrocarbon group containing a hydroxy group, asulfo group, a carboxy group, or the like.

X represents a hydrogen atom, sodium, potassium, ammonium,diethanolamine, or triethanolamine, with sodium, ammonium, adiethanolamine, or triethanolamine being preferable.

Hereinafter, preferable specific examples [Exemplified Compounds (P-1)to (P-28)] of an anionic surfactant that include the compoundsrepresented by Formulae (II) to (V) and that can be preferably used inthe invention are shown, but the invention is not limited thereto.

In the following Exemplified Compounds, the degree of polymerization nor m of a polymer is 1 to 5, and, x and y in the Exemplified CompoundP-4 satisfy that x+y=10 and x is 1 to 5. p in the Exemplified CompoundP-2 is 1 to 3. In the following structures, “H.Na” represents a sulfonicacid compound or a sodium salt thereof.

As an anionic surfactant contained in the polishing liquid of theinvention, from the viewpoint of achieving a favorable selectivity, P-2,P-3, P-4, P-10, P-13, P-15, P-17, P-19, P-20, P-21, P-22, P-24, P-26, orP-27 is preferable and P-2, P-4, P-13, P-15, P-17, P-20, P-21, P-22,P-24, or P-26 is more preferable, among the compounds represented byFormulae (II), (III), (IV), and (V).

The anionic surfactant contained in the polishing liquid may be onekind, or two or more kinds thereof may be used in combination.

The total amount of the anionic surfactant contained in the polishingliquid is preferably 0.00001% by mass to 1% by mass, more preferably0.0001% by mass to 1% by mass, and still more preferably 0.0005% by massto 0.1% by mass based on the total mass of the polishing liquid whenused for polishing.

[Other Components]

(pH Adjustor)

The polishing liquid of the invention has a pH of 1.5 to 7.0. It ispreferable that the pH be in the range of 2.5 to 7.0. The polishingliquid of the invention provides excellent effects when the pH is inthis range.

In order to adjust the pH of the polishing liquid within theabove-mentioned range, alkali/acid or a buffer may be used.

Preferable examples of the alkali/acid or the buffer includenon-metallic alkali agents such as ammonia, ammonium hydroxide, organicammonium hydroxides such as tetramethylammonium hydroxide, alkanolaminessuch as diethanolamine, triethanolamine and tri-isopropanolamine, alkalimetal hydroxides such as sodium hydroxide, potassium hydroxide andlithium hydroxide, inorganic acids such as nitric acid, sulfuric acidand phosphoric acid, carbonate such as sodium carbonate, phosphate suchas trisodium phosphate, borate, tetraborate, and hydroxybenzoate.Examples of particularly preferable alkali agents include ammoniumhydroxide, potassium hydroxide, lithium hydroxide, andtetramethylammonium hydroxide.

The addition amount of the alkali/acid or the buffer may be an amount inwhich the pH is maintained in a preferable range. The amount is in therange of preferably 0.0001 mol to 1.0 mol and more preferably 0.003 molto 0.5 mol per 1 L of the polishing liquid when used for polishing.

(Corrosion Inhibitor)

The polishing liquid of the invention may contain a corrosion inhibitorthat adheres to the surface to be polished to form a film to therebycontrol the corrosion of the surface of metal. It is preferable for thecorrosion inhibitor in the invention to contain a heterocyclic aromaticcompound having 3 or more nitrogen atoms in the molecule and having acondensed ring structure. Here, the “3 or more nitrogen atoms” ispreferably atoms forming a condensed ring. As such a heterocyclicaromatic compound, benzotriazole and derivatives obtained by introducingvarious substituents into benzotriazole are preferable.

Examples of the corrosion inhibitor include benzotriazole,1,2,3-benzotriazole, 5,6-dimethyl-1,2,3-benzotriazole,1-(1,2-dicarboxyethyl)benzotriazole,1-[N,N-bis(hydroxyethyl)aminomethyl]benzotriazole, and1-(hydroxymethyl)benzotriazole. In particular, it is more preferablethat the corrosion inhibitor be selected from 1,2,3-benzotriazole,5,6-dimethyl-1,2,3-benzotriazole, 1-(1,2-dicarboxyethyl)benzotriazole,1-[N,N-bis(hydroxyethyl)aminomethyl]benzotriazole, and1-(hydroxymethyl)benzotriazole.

The addition amount of such a corrosion inhibitor is in the range ofpreferably 0.01% by mass to 0.2% by mass and more preferably 0.05% bymass to 0.2% by mass based on the mass of the polishing liquid when usedfor polishing. More specifically, the addition amount of such acorrosion inhibitor is preferably 0.01% by mass or more from theviewpoint of not increasing dishing but is preferably 0.2% by mass orlower from the viewpoint of storage stability.

(Chelating Agent)

In order to reduce adverse effects due to an intermixed polyvalent metalion or the like, the polishing liquid of the invention preferablycontains a chelating agent (i.e., water softener) as required.

As the chelating agent, a widely used water softener which is aprecipitation-preventing agent of calcium or magnesium, and a relativecompound thereof, are mentioned. Examples include nitrilotriacetic acid,diethylenetriamine pentaacetic acid, ethylenediamine tetraacetic acid,N,N,N-amino trimethylene phosphonic acid, ethylenediamine-N,N,N′,N′-tetramethylene sulfonic acid, transcyclohexanediaminetetraacetic acid, 1,2-diaminopropane tetraacetic acid,glycoletherdiamine tetraacetic acid, ethylenediamine ortho-hydroxyphenylacetic acid, ethylenediamine disuccinic acid (SS isomer),N-(2-carboxylate ethyl)-L-asparatic acid, β-alaninediacetic acid,2-phosphonobutane-1,2,4-tricarboxylic acid,1-hydroxyethylidene-1,1-diphosphonic acid,N,N′-bis(2-hydroxybenzyl)ethylene diamine-N,N′-diacetic acid, and1,2-dihydroxybenzene-4,6-disulfonic acid.

With respect to the chelating agent, two or more kinds may be used incombination as required.

The addition amount of the chelating agent may be an amount sufficientfor sequestering metal ions, such as intermixed polyvalent metal ions orthe like. For example, the chelating agent is added in an amount of0.0003 mol to 0.07 mol per 1 L of the polishing liquid when used forpolishing.

[Body to be Polished]

The body to be polished to which the polishing liquid of the inventionis applied is a body to be polished containing at least a first layercontaining polysilicon or modified polysilicon and a second layercontaining at least one selected from the group consisting of siliconoxide, silicon nitride, silicon carbide, silicon carbonitride, siliconoxycarbide, and silicon oxynitride. More specifically, the body to bepolished is preferably used when polysilicon or modified polysilicon isused as an electrode material and a gate electrode in a semiconductorintegrated circuit is formed by CMP.

Examples of the “modified polysilicon” in the invention include siliconin which impurity elements, such as B or P, have been doped inpolysilicon.

Usually, when the gate electrode is formed, the first layer is formed byforming a layer containing silicon oxide or the like on the surface of asubstrate, forming a concave portion on the layer by etching or thelike, and charging the formed concave portion with polysilicon ormodified polysilicon. Next, the second layer containing at least oneselected from the group consisting of silicon oxide, silicon nitride,silicon carbide, silicon carbonitride, silicon oxycarbide, and siliconoxynitride is formed as a barrier layer on the surface of the firstlayer.

In CMP for the formation of the gate electrode, when polishing startsfrom the surface of the second layer, and then the polishing of thesecond layer is advanced to expose the surface of the first layer, thepolishing rate rapidly decreases, whereby the completion of thepolishing of the second layer is detected, and thus excessive polishingof the surface of the polysilicon or modified polysilicon used for thegate electrode is suppressed. The modified polysilicon refers topolysilicon in which impurities, such as B or P, have been doped inpolysilicon.

Thereafter, the gate electrode is formed by removing, by etching,portions other than the polysilicon or modified polysilicon thatfunctions as an electrode and the required silicon oxide layer of theperiphery thereof.

[Polishing Method]

The polishing method of the invention comprises supplying the abovementioned polishing liquid of the invention to a polishing pad on apolishing platen, rotating the polishing platen, and thereby causingrelative motion of the polishing pad and a surface to be polished of abody to be polished while in contact with each other for carrying outpolishing.

The polishing liquid of the invention may be: a concentrated liquid,which is diluted with water or an aqueous solution when used (Case 1);prepared by mixing respective components in the form of an aqueoussolution mentioned in the following section and optionally diluting withwater (Case 2); and a liquid which can be used as it is for carrying outpolishing (Case 3). The polishing liquid of any of the above-describedcases can be applied to the polishing method of the invention.

As an apparatus used for polishing, a common polishing apparatus havinga holder that holds a body to be polished having a surface to bepolished (e.g., a wafer on which a conductive material film is formed)and a polishing platen (to which a motor in which the number ofrotations can be changed is attached) to which a polishing pad isattached can be used. As the polishing pad, a common nonwoven fabric,foamed polyurethane, porous fluororesin, or the like can be used, andthere is no limitation on the polishing pad. There is no limitation onpolishing conditions, but the rotation rate of the polishing platen ispreferably as low as 200 rpm or lower so that the body to be polisheddoes not jump out. The pressing pressure of the body to be polishedhaving a surface to be polished (film to be polished) against thepolishing pad is preferably 0.68 to 34.5 kPa. In order to satisfy thein-plane uniformity in polishing rate of the body to be polished and theflatness of a pattern, the pressing pressure is more preferably 3.40 to20.7 kPa.

While polishing, the polishing liquid is successively supplied to thepolishing pad with a pump or the like.

The body to be polished after the completion of polishing issufficiently washed in running water, and then dried after removingwater drops adhering onto the body to be polished using a spin dryer orthe like.

In the invention, when a concentrated liquid is diluted as in the methoddescribed in case 1 above, the following aqueous solution can be used.The aqueous solution is water containing at least one of oxidizers,organic acids, additives, and surfactants beforehand. The sum ofcomponents contained in the aqueous solution and components contained ina concentrated liquid to be diluted will be the components of apolishing liquid which is used for polishing.

Thus, when a concentrated liquid is diluted with an aqueous solution andthen used, a further concentrated liquid can be prepared becausecomponents that are difficult to dissolve can be blended later in theform of an aqueous solution.

As a method for adding water or an aqueous solution to a concentratedliquid for dilution, there is a method including mixing a concentratedpolishing liquid and water or an aqueous solution by connecting a pipeline for supplying the concentrated polishing liquid and a pipe line forsupplying water or an aqueous solution, and supplying the mixed anddiluted polishing liquid to the polishing pad. For mixing of aconcentrated liquid and water or an aqueous solution, generallyperformed methods, such as a method including passing the concentratedliquid and water or the aqueous solution through a narrow passage underthe application of a pressure for collisional mixing thereof, a methodincluding repeatedly diverting/separating and joining the flow of eachof the concentrated liquid and water or the aqueous solution by stuffingthe pipe line with a filling such as a glass tube, or a method includingproviding a blade that rotates under power to the pipe line, areemployable.

The supply rate of the polishing liquid is preferably 10 to 1000 ml/min,and, in order to satisfy the in-plane uniformity in polishing rate ofthe body to be polished and the flatness of a pattern, is morepreferably 170 to 800 ml/min.

Furthermore, as a method for polishing while diluting a concentratedliquid with water or an aqueous solution, there is a method includingindependently providing a pipe line for supplying a polishing liquid anda pipe line for supplying water or an aqueous solution, supplying givenamounts of the polishing liquid and water or the aqueous solution to apolishing pad from each pipe line, and carrying out polishing whilemixing by causing relative motion of the polishing pad and the surfaceto be polished. Moreover, a method including adding given amounts of theconcentrated liquid and water or the aqueous solution in one containerfor mixing, supplying the mixed polishing liquid to a polishing pad, andthen carrying out polishing can also be employed.

Moreover, as another polishing method, there is a method includingdividing components to be contained in the polishing liquid into atleast two constituents, diluting them by adding water or an aqueoussolution before use, supplying them to a polishing pad on a polishingplaten, and bringing the polishing pad into contact with the surface tobe polished to cause relative motion of the surface to be polished andthe polishing pad for carrying out polishing.

Moreover, additives with low solubility are divided into twoconstituents (A) and (B). For example, oxidizers, additives, andsurfactants are classified into the constituent (A) and organic acids,additives, surfactants, and water are classified into the constituent(B). Then, when they are used, water or an aqueous solution is added fordiluting the constituents (A) and (B).

In the case of the above example, three pipe lines for separatelysupplying the constituent (A), the constituent (B), and water or anaqueous solution are required. For dilution mixing, there is a methodincluding connecting the three pipe lines to one pipe line for supplyingthem to a polishing pad, and then mixing them in the pipe line. In thiscase, the two pipe lines are connected, and then another one pipe linecan be connected thereto. Specifically, a method including mixingconstituents containing additives that are hard to dissolve and otherconstituents, lengthening a mixing path for securing a dissolving time,and then connecting a pipe line for water or an aqueous solution ismentioned.

As other mixing methods, there is a method including directly leadingthe three pipe lines to a polishing pad, and mixing by relative motionof the polishing pad and the surface to be polished or a method ofmixing the three constituents in one container, and supplying a dilutedpolishing liquid to the polishing pad therefrom, as described above.

In the above-described polishing method, when one constituent containingan oxidizer is adjusted to 40° C. or less, other constituents are heatedin the range of from room temperature to 100° C., and then the oneconstituent and the other constituents are mixed or diluted by addingwater or an aqueous solution, the solution temperature can be adjustedto 40° C. or lower. This method is preferable for increasing thesolubility of a raw material with low solubility of the polishing liquidby utilizing a phenomenon in which the solubility becomes high at hightemperatures.

A raw material that has been dissolved by heating the above-mentionedother constituents in the range of from room temperature to 100° C.precipitates in the solution when the temperature decreases. Therefore,when the other constituents having low temperatures are used, theprecipitated raw material needs to be dissolved by heating beforehand.For the above, a method including supplying the other constituents inwhich the raw materials have been dissolved by heating and a methodincluding stirring a solution containing a precipitate, supplying thesolution, and dissolving the precipitate by heating a pipe line can beemployed. There is a possibility that an oxidizer decomposes when theheated other constituents increase the temperature of the oneconstituent containing an oxidizer to 40° C. or more. Thus, when theheated other constituents and the one constituent containing an oxidizerare mixed, the temperature of the mixture is preferably adjusted to 40°C. or lower.

Thus, in the invention, the components of the polishing liquid may bedivided to two or more, and then the divided components may be suppliedto the surface to be polished. In this case, the components of thepolishing liquid are preferably divided to components containingoxidizers and components containing organic acids, and then supplied.Moreover, the polishing liquid may be formed into a concentrated liquid,and then supplied to the surface to be polished while separatelysupplying a dilution water.

In the invention, when a method including dividing the components of thepolishing liquid to two or more, and then supplying them to the surfaceto be polished is applied, the supply amount indicates the total amountof the components supplied from the respective pipe lines.

[Pad]

As the polishing pad for polishing that can be applied to the polishingmethod of the invention, a non-foamed pad or a foamed pad may be used.In the former, a hard synthetic resin bulk material, such as a plasticsheet, is used for the pad. Examples of the latter include anindependent foamed body (dry foamed type), a continuous foamed body (wetfoamed type), and a two-layer composite (lamination type). Inparticular, the two-layer composite (lamination type) is preferable. Thefoaming may be uniform or non-uniform.

The pad may contain abrasive grains (e.g., ceria, silica, alumina, andresin) generally used for polishing. Examples of the pad are classifiedinto soft type and hard type, and any of them may be acceptable. In thelamination type, each layer is preferably different in hardness. Asmaterials, a nonwoven fabric, artificial leather, polyamide,polyurethane, polyester, polycarbonate, and the like are preferable. Onthe surface in contact with the surface to be polished, a gratinggroove, a hole, a concentric groove, a spiral groove, or the like may beformed.

[Wafer]

The diameter of a wafer as the body to be polished to which CMP isperformed with the polishing liquid in the invention is preferably 200mm or more and particularly preferably 300 mm or more. When the diameteris 300 mm or more, the effects of the invention may be notably provided.

[Polishing Apparatus]

There is no limitation on an apparatus capable of polishing using thepolishing liquid of the invention. Examples include, but not limitedthereto, MA-300D (manufactured by Musashino Denshi Co.), Mirra Mesa CMPand Reflexion CMP (manufactured by Applied Materials), FREX200 andFREX300 (manufactured by Ebara Corporation), NPS3301 and NPS2301(manufactured by NIKON), A-FP-310A and A-FP-210A (manufactured by TokyoSeimitsu), 2300 TERES (manufactured by Ram Research), and Momentum(manufactured by Speedfam IPEC).

According to the invention, for example, the following exemplifiedembodiments <1> to <10> are provided.

<1>A polishing liquid which is used for chemical mechanical polishing ofa body to be polished in a planarization process for manufacturing of asemiconductor integrated circuit, the body to be polished comprising atleast a first layer containing polysilicon or modified polysilicon and asecond layer containing at least one selected from the group consistingof silicon oxide, silicon nitride, silicon carbide, siliconcarbonitride, silicon oxycarbide, and silicon oxynitride,

the polishing liquid having a pH of 1.5 to 7.0, comprising (1) colloidalsilica particles, (2) an organic acid, and (3) an anionic surfactant,and being capable of selectively polishing the second layer with respectto the first layer.

<2> The polishing liquid according to <1>, which is capable of polishingthe body to be polished at a ratio represented by RR(other)/RR(p-Si) inthe range of 1.5 to 200 wherein RR(p-Si) represents a polishing rate ofthe first layer and RR(other) represents a polishing rate of the secondlayer.

<3> The polishing liquid according to <1> or <2>, wherein theconcentration of the colloidal silica is 0.1% by mass to 10% by massbased on the total mass of the polishing liquid.

<4> The polishing liquid according to any one of <1> to <3>, wherein thecolloidal silica has an average primary particle diameter of 5 nm to 100nm and an average secondary particle diameter of 10 nm to 300 nm.

<5> The polishing liquid according to any one of <1> to <4>, wherein theorganic acid contains at least one carboxyl group in a moleculestructure thereof.

<6> The polishing liquid according to any one of <1> to <5>, wherein theorganic acid is represented by the following Formula (I),

HOOC—R—COOH   (I)

wherein R represents an alkylene group having 1 to 20 carbon atoms, analkynylene group, a cycloalkylene group, an arylene group, or a groupobtained by combining two or more thereof. These groups may further haveother substituents.

<7> The polishing liquid according to any one of <1> to <6>, wherein theconcentration of the organic acid is 0.001% by mass to 3% by mass basedon the total mass of the polishing liquid.

<8> The polishing liquid according to any one of <1> to <7>, wherein theanionic surfactant is at least one compound selected from the groupconsisting of compounds represented by the following Formulae (II),(III), (IV), and (V),

R¹—O—SO₃X   Formula (II)

wherein in Formula (II), R¹ represents an alkyl group having 6 to 30carbon atoms, an alkenyl group, a cycloalkyl group, an aryl group, anaralkyl group, or a group obtained by combining two or more thereof, andX represents a hydrogen atom, sodium, potassium, ammonium,diethanolamine, or triethanolamine,

R²—O—(CH₂CH₂O)_(n)—SO₃X   Formula (III)

wherein in Formula (III), R² represents an alkyl group having 6 to 30carbon atoms, an alkenyl group, a cycloalkyl group, an aryl group, anaralkyl group, or a group obtained by combining two or more thereof, nrepresents an integer of 1 to 10, and X represents a hydrogen atom,sodium, potassium, ammonium, diethanolamine, or triethanolamine,

wherein in Formula (IV), R³ represents an alkyl group having 6 to 30carbon atoms, an alkenyl group, a cycloalkyl group, an aryl group, anaralkyl group, or a group obtained by combining two or more thereof, Xrepresents a hydrogen atom, sodium, potassium, ammonium, diethanolamine,or triethanolamine, and a plurality of Xs may be the same or differentfrom each other, and

wherein in Formula (V), R⁴ represents an alkylene group having 1 to 20carbon atoms, an alkynylene group, a cycloalkylene group, an arylenegroup, an alkylene oxide group, or a group obtained by combining two ormore thereof, R⁵ to R⁹ each independently represent a hydrogen atom, ahydroxy group, an alkyl group having 1 to 30 carbon atoms, an alkenylgroup, a cycloalkyl group, an aryl group, an aralkyl group, a sulfogroup, a carboxyl group, or a hydrocarbon group containing any of thesegroups, and X represents a hydrogen atom, sodium, potassium, ammonium,diethanolamine, or triethanolamine.

<9> The polishing liquid according to any one of <1> to <8>, wherein theconcentration of the anionic surfactant is 0.001% by mass to 1% by massbased on the total mass of the polishing liquid.

<10> A polishing method comprising supplying the polishing liquidaccording to any one of <1> to <9> to a polishing pad on a polishingplaten, rotating the polishing platen, and thereby causing relativemotion of the polishing pad and a surface to be polished of a body to bepolished while in contact with each other for carrying out polishing.

Therefore, the invention can provide a polishing liquid that can be usedfor chemical mechanical polishing of a body to be polished having alayer containing polysilicon or modified polysilicon in themanufacturing of a semiconductor integrated circuit, has a highpolishing rate, and can selectively suppress polishing of the layercontaining polysilicon or modified polysilicon, and a polishing methodusing the same.

EXAMPLES

Hereinafter, the invention will be more specifically described withreference to Examples, but is not limited to the following Examples.

Examples 1-1 to 1-5, Comparative Examples 1-1 to 1-3

<Preparation of Polishing Liquid>

Polishing liquids (polishing liquids of Examples 1-1 to 1-5 andComparative Examples 1-1 to 1-3) having the following composition and pHwere prepared, and then a wafer having a polysilicon film was polished.Then, the pH dependency of the polishing rate in the polishing of apolysilicon layer (p-Si layer) was evaluated.

Polishing Liquid Composition

Colloidal silica particles: A1 200 g/L Organic acid: Citric acid 0.5 g/LAnionic surfactant: P-21 0.05 g/L Total amount to which pure water wasadded 1,000 mL (pH (adjusted with aqueous ammonia and nitric pH shown inTable 2) acid)

The shapes and the particle diameters of the colloidal silica particles(A1 to A5) used for each Example in this specification are as shown inTable 1.

TABLE 1 Abrasive grain name [Average primary particle diameter (nm),Shape] A1 PL3 [35 nm, cocoon-shaped] A2 PL3L [35 nm, spherical] A3 PL3H[35 nm, aggregate] A4 PL2 [25 nm, cocoon-shaped] A5 PL2L [20 nm,spherical]

Evaluation was performed using the polishing liquids of Examples 1-1 to1-5 and Comparative Examples 1-1 to 1-3. The evaluation method is asfollows.

<Evaluation Method>

(Polishing Apparatus)

Each wafer film shown below was polished using “MA-300D” manufactured byMusashino Electronics Co., Ltd. as a polishing apparatus while supplyinga slurry under the following conditions.

Number of rotations of table: 112 rpm Number of rotations of head: 113rpm Polishing pressure: 18.4 kPa Polishing pad: IC1400 XY-K-Padmanufactured by Rodel Nitta Co. Polishing liquid supply rate: 50 ml/min

(Body to be Polished)

As a body to be polished, a 6 cm×6 cm cut wafer cut out from an 8-inchwafer in which a polysilicon film was formed on an Si substrate wasused.

(Evaluation of Polishing Rate)

The layer thickness (nm) before and after polishing of the polysiliconlayer (p-Si layer) was measured, and the polishing rate was calculatedusing the following equation.

Polishing rate (nm/minute)=(Layer thickness before polishing−Layerthickness after polishing)/Polishing time

The layer thickness was measured by a non-contact layer thickness meterFE-33 (manufactured by Otsuka Electronics Co., Ltd.).

The obtained results are shown in Table 2. FIG. 1 is a graph showingchanges in polishing rate of polysilicon (p-Si) when the pH of thepolishing liquid of Example 1 was varied.

TABLE 2 p-Si polishing rate pH (nm/min) Example 1-1 1.5 35.0 Example 1-22 30.0 Example 1-3 3.5 20.0 Example 1-4 5 15.0 Example 1-5 7 28.0Comparative Example 1-1 8 42.3 Comparative Example 1-2 9 50.0Comparative Example 1-3 10 66.0

As shown in Table 2, the following points were confirmed. In thepolishing liquids of Examples 1-1 to 1-5 as the polishing liquid of theinvention, the polishing rate with respect to the polysilicon layer issuppressed and is notably suppressed particularly when the pH is in therange of 2 to 7. However, when the pH is lower than 1.5 or exceeds 7, atendency that the polishing rate with respect to the polysilicon layerincreases is observed. In particular, in the polishing liquids ofComparative Examples 1-1 to 1-3 which are outside the scope of thepolishing liquid of the invention, the polishing rate with respect tothe polysilicon layer remarkably increases in comparison with thepolishing liquid of each Example. This confirmed that it is essentialfor the polishing liquid of the invention to have a pH in the range of1.5 to 7 from the viewpoint of specific polishing inhibition withrespect to the polysilicon layer.

Example 2

<Preparation of Polishing Liquid>

A polishing liquid (polishing liquid of Example 2) having the followingcomposition and pH was prepared.

Composition 1

Colloidal silica particles: A1 200 g/L Organic acid: Citric acid 0.5 g/LAnionic surfactant: P-1 0.05 g/L Total amount to which pure water wasadded 1,000 mL (pH (adjusted with aqueous ammonia and nitric acid) 5.0)

Polishing evaluation was performed using the polishing liquid of Example2.

<Evaluation Method>

(Polishing Apparatus)

Each wafer film shown below was polished using “MA-300D” manufactured byMusashino Electronics Co., Ltd. as a polishing apparatus while supplyinga slurry under the following conditions.

Number of rotations of table: 112 rpm Number of rotations of head: 113rpm Polishing pressure: 18.4 kPa Polishing pad: IC1400 XY-K-Padmanufactured by Rodel Nitta Co. Polishing liquid supply rate: 50 ml/min

Body to be Polished

As a body to be polished, a 6 cm×6 cm cut wafer cut out from 8-inchwafer in which a polysilicon layer (p-Si layer), a silicon oxide layer(SiO₂ layer), and a silicon nitride layer (Si₃N₄ layer) was formed on anSi substrate was used.

Polishing Rate, Polishing Rate Ratio

The layer thickness (nm) before and after polishing of each of thepolysilicon layer (p-Si layer), the silicon oxide layer (SiO₂-layer),and the silicon nitride layer (Si₃N₄ layer) was measured, and thepolishing rate was calculated using the following equation. The layerthickness was measured by a non-contact layer thickness meter FE-33(manufactured by Otsuka Electronics Co., Ltd.).

Polishing rate (nm/minute)=(Layer thickness before polishing−Layerthickness after polishing)/Polishing time

The polishing rate ratio represented by RR(other)/RR(p-Si) wascalculated for the p-Si layer and the SiO₂-layer, and the p-Si layer andthe Si₃N₄ layer.

The obtained results are shown in Tables 3 and 4.

Examples 3 to 29 and Comparative Examples 1 to 4

The polishing liquids were prepared substantially in the same manner asin the preparation of the polishing liquid of Example 2, except forchanging the colloidal silica particles, the anionic surfactant, and theorganic acid to the components listed in Tables 3 and 4 and adjustingthe pH to the shown values. The obtained polishing liquids of Examples 2to 29 and Comparative Examples 1 to 4 were evaluated in the same manneras in Example 1, and the experimental results thereof were shown inTables 3 and 4.

Abrasive particles A1 to A5 are as shown in Table 1.

TABLE 3 Colloidal silica Anionic p-Si polishing SiO₂ Si₃N₄ PolishingPolishing particles Organic acid surfactant rate polishing ratepolishing rate selectivity selectivity (content) (Content) (Content) pH(nm/min) (nm/min) (nm/min) (SiO₂/p-Si) (Si₃N₄/p-Si) Example 2 A1 (200g/L) Citric acid P-1 5.0 10 27 40 2.70 4.00 (0.5 g/L) (0.05 g/L) Example3 A1 (100 g/L) Diglycolic acid P-2 5.0 8 25 45 3.13 5.63 A4 (20 g/L)(0.5 g/L) (0.05 g/L) Example 4 A1 (100 g/L) Malic acid P-3 5.0 12 20 351.67 2.92 A3 (100 g/L) (0.5 g/L) (0.15 g/L) Example 5 A2 (200 g/L) EDTAP-4 5.0 12 19 38 1.58 3.17 (0.5 g/L) (0.05 g/L) Example 6 A3 (150 g/L)Oxalic acid P-5 5.0 15 21 42 1.40 2.80 (0.5 g/L) (0.20 g/L) Example 7 A1(100 g/L) Malic acid P-6 5.0 12 25 44 2.08 3.67 A2 (100 g/L) (0.5 g/L)(0.05 g/L) Example 8 A4 (100 g/L) EDTA P-7 5.0 9 32 39 3.56 4.33 (0.5g/L) (0.05 g/L) Example 9 A1 (100 g/L) Adipic acid P-8 5.0 5 30 38 6.007.60 A2(100 g/L) (0.5 g/L) (0.05 g/L) Example 10 A1 (100 g/L) Maleicacid P-9 5.0 12 37 35 3.08 2.92 A4 (20 g/L) (0.5 g/L) (0.1 g/L) Example11 A3 (80 g/L) Citric acid P-10 5.0 11 43 33 3.91 3.00 (0.5 g/L) (0.05g/L) Example 12 A1 (100 g/L) Citric acid P-11 5.0 14 47 31 3.36 2.21(0.5 g/L) (0.05 g/L) Example 13 A1 (100 g/L) Citric acid P-12 5.0 16 4554 2.81 3.38 A2 (20 g/L) (0.5 g/L) (0.05 g/L) Example 14 A5 (150 g/L)Diglycolic acid P-13 5.0 15 37 36 2.47 2.40 (0.5 g/L) (0.05 g/L) Example15 A1 (100 g/L) Citric acid P-14 5.0 12 32 45 2.67 3.75 (0.5 g/L) (0.3g/L) Example 16 A3 (100 g/L) Adipic acid P-15 5.0 3 31 42 10.33 14.00(0.5 g/L) (0.05 g/L)

TABLE 4 Colloidal silica Anionic p-Si polishing SiO₂ Si₃N₄ PolishingPolishing particles Organic acid surfactant rate polishing ratepolishing rate selectivity selectivity (content) (Content) (Content) pH(nm/min) (nm/min) (nm/min) (SiO₂/p-Si) (Si₃N₄/p-Si) Example 17 A1 (100g/L) Malic acid P-16 5.0 15 38 40 2.53 2.67 A4 (20 g/L) (0.5 g/L) (0.05g/L) Example 18 A4 (200 g/L) EDTA P-17 5.0 12 33 35 2.75 2.92 (0.5 g/L)(0.05 g/L) Example 19 A1 (200 g/L) Diglycolic acid P-18 5.0 14 36 412.57 2.93 (0.5 g/L) (0.05 g/L) Example 20 A1 (100 g/L) Citric acid P-195.0 2 55 60 27.50 30.00 A4 (20 g/L) (0.5 g/L) (0.05 g/L) Example 21 A3(80 g/L) Adipic acid P-20 5.0 12 37 45 3.08 3.75 (0.5 g/L) (0.45 g/L)Example 22 A3 (80 g/L) Citric acid P-21 5.0 11 43 37 3.91 3.36 (0.5 g/L)(0.05 g/L) Example 23 A1 (100 g/L) Citric acid P-22 5.0 14 47 39 3.362.79 (0.5 g/L) (0.05 g/L) Example 24 A1 (100 g/L) Oxalic acid P-23 5.016 45 50 2.81 3.13 A2 (20 g/L) (0.5 g/L) (0.05 g/L) Example 25 A2 (150g/L) Diglycolic acid P-24 5.0 15 37 26 2.47 1.73 (0.5 g/L) (0.20 g/L)Example 26 A1 (100 g/L) Maleic acid P-25 5.0 12 32 36 2.67 3.00 (0.5g/L) (0.05 g/L) Example 27 A1 (100 g/L) Citric acid P-26 5.0 3 31 3010.33 10.00 A4 (20 g/L) (0.5 g/L) (0.05 g/L) Example 28 A1 (200 g/L)Oxalic acid P-27 5.0 15 38 35 2.53 2.33 (0.5 g/L) (0.10 g/L) Example 29A4 (200 g/L) Diglycolic acid P-28 5.0 12 33 25 2.75 2.08 (0.5 g/L) (0.05g/L) Comparative A1 (200 g/L) Citric acid — 5.0 26 30 30 1.15 1.15Example 1 (0.5 g/L) Comparative A1 (200 g/L) Citric acid — 10.0 56 35 120.63 0.21 Example 2 (0.5 g/L) Comparative — Citric acid P-1 5.0 7 3 20.43 0.29 Example 3 (0.5 g/L) (0.05 g/L) Comparative A1 (200 g/L) — P-15.0 18 10 4 0.56 0.22 Example 4 (0.05 g/L)

As is clear from Tables 3 and 4, it is revealed that, by using thepolishing liquids of the Examples, excessive polishing of thepolysilicon layer is suppressed because the polishing rates of siliconoxide and silicon nitride are high and polishing of the polysiliconlayer is selectively suppressed.

All publications, patent applications, and technical standards mentionedin this specification are herein incorporated by reference to the sameextent as if each individual publication, patent application, ortechnical standard was specifically and individually indicated to beincorporated by reference.

1. A polishing liquid which is used for chemical mechanical polishing of a body to be polished in a planarization process for manufacturing of a semiconductor integrated circuit, the body to be polished comprising at least a first layer containing polysilicon or modified polysilicon and a second layer containing at least one selected from the group consisting of silicon oxide, silicon nitride, silicon carbide, silicon carbonitride, silicon oxycarbide, and silicon oxynitride, the polishing liquid having a pH of 1.5 to 7.0, comprising (1) colloidal silica particles, (2) an organic acid, and (3) an anionic surfactant, and being capable of selectively polishing the second layer with respect to the first layer.
 2. The polishing liquid according to claim 1, which is capable of polishing the body to be polished at a ratio represented by RR(other)/RR(p-Si) in the range of 1.5 to 200 wherein RR(p-Si) represents a polishing rate of the first layer and RR(other) represents a polishing rate of the second layer.
 3. The polishing liquid according to claim 1, wherein the concentration of the colloidal silica is 0.1% by mass to 10% by mass based on the total mass of the polishing liquid.
 4. The polishing liquid according to claim 1, wherein the colloidal silica has an average primary particle diameter of 5 nm to 100 nm and an average secondary particle diameter of 10 nm to 300 nm.
 5. The polishing liquid according to claim 1, wherein the organic acid contains at least one carboxyl group in a molecule structure thereof.
 6. The polishing liquid according to claim 1, wherein the organic acid is represented by the following Formula (I), HOOC—R—COOH   (I) wherein R represents an alkylene group having 1 to 20 carbon atoms, an alkynylene group, a cycloalkylene group, an arylene group, or a group obtained by combining two or more thereof.
 7. The polishing liquid according to claim 1, wherein the concentration of the organic acid is 0.001% by mass to 3% by mass based on the total mass of the polishing liquid.
 8. The polishing liquid according to claim 1, wherein the anionic surfactant is at least one compound selected from the group consisting of compounds represented by the following Formulae (II), (III), (IV), and (V), R¹—O—SO₃X   Formula (II) wherein in Formula (II), R¹ represents an alkyl group having 6 to 30 carbon atoms, an alkenyl group, a cycloalkyl group, an aryl group, an aralkyl group, or a group obtained by combining two or more thereof, and X represents a hydrogen atom, sodium, potassium, ammonium, diethanolamine, or triethanolamine, R²—O—(CH₂CH₂O)_(n)—SO₃X   Formula (III) wherein in Formula (III), R² represents an alkyl group having 6 to 30 carbon atoms, an alkenyl group, a cycloalkyl group, an aryl group, an aralkyl group, or a group obtained by combining two or more thereof, n represents an integer of 1 to 10, and X represents a hydrogen atom, sodium, potassium, ammonium, diethanolamine, or triethanolamine,

wherein in Formula (IV), R³ represents an alkyl group having 6 to 30 carbon atoms, an alkenyl group, a cycloalkyl group, an aryl group, an aralkyl group, or a group obtained by combining two or more thereof, X represents a hydrogen atom, sodium, potassium, ammonium, diethanolamine, or triethanolamine, and a plurality of Xs may be the same or different from each other, and

wherein in Formula (V), R⁴ represents an alkylene group having 1 to 20 carbon atoms, an alkynylene group, a cycloalkylene group, an arylene group, an alkylene oxide group, or a group obtained by combining two or more thereof, R⁵ to R⁹ each independently represent a hydrogen atom, a hydroxy group, an alkyl group having 1 to 30 carbon atoms, an alkenyl group, a cycloalkyl group, an aryl group, an aralkyl group, a sulfo group, a carboxyl group, or a hydrocarbon group containing any of these groups, and X represents a hydrogen atom, sodium, potassium, ammonium, diethanolamine, or triethanolamine.
 9. The polishing liquid according to claim 1, wherein the concentration of the anionic surfactant is 0.001% by mass to 1% by mass based on the total mass of the polishing liquid.
 10. A polishing method comprising supplying the polishing liquid according to claim 1 to a polishing pad on a polishing platen, rotating the polishing platen, and thereby causing relative motion of the polishing pad and a surface to be polished of a body to be polished while in contact with each other for carrying out polishing. 